In the field of microelectronics, future applications require not only an increase in the computing performance or in the storage capacity of an IC component (IC=integrated circuit) but also an extension of the functionality thereof. Such an extension of functionality comprises e.g. the possibility of combining sensor technology, data processing and data storage on one chip component, e.g. for a CCD chip (CCD=charge coupled device), which is integrated directly on one logic level for evaluating and reducing large amounts of data. Starting from the planar standard CMOS technology, efforts concerning the development of a vertical connection technique are therefore increasingly made so as to fulfill the future system requirements in the field of microelectronics.
The desired option, viz. that also wafers with sensitive surface structures can vertically be integrated with a second wafer, makes it necessary to possess a connection technique permitting a wafer bottom and a wafer top to be placed one on top of the other, i.e. to be permanently connected. In the field of technology, it is known to connect surfaces of bodies, which consist of plasma oxide, thermal oxide and silicon, with polyimide.
The only material that can be used for a CMOS-compatible electric connection of two mechanically connected wafers is tungsten which is deposited in a CVD process (CVD=chemical vapour deposition) from the gaseous phase (WF.sub.6) at 400 to 450.degree. C. This deposition of tungsten can only be carried out after the mechanical connection of the two wafers. This means, in turn, that for the mechanical connection of the wafers a method must be found which provides a mechanical connection of said wafers that is capable of resisting temperatures of up to 450.degree. C.
Conventional adhesive materials are not suitable for establishing a connection of the above-mentioned kind, which is capable of resisting temperatures of up to 450.degree. C., since said materials are not sufficiently temperature stable. Furthermore, conventional adhesive materials cannot be applied to the wafers with the necessary homogeneity in the range of from approx. 1 to 3 .mu.m thickness. The temperature requirement prevents the use of organic adhesives, the homogeneity requirement prevents the use of mineral-matter-filled, inorganic adhesives for establishing a permanent mechanical connection between two wafers.